The present invention relates to a method and apparatus for microwave etching and deposition. The invention provides for the use of remote microwave injection into the chamber housing the article being processed. One known method for such processing is referred to as gas reactive ion etching (RIE). In accordance with such process, the article to be etched and a reaction gas are brought into contact with each other to etch the article. This invention relates to the microwave generating components and the reactant gas conduits utilized in such processes.
Microwave discharge has found increasing application as an excitation source for the production of free radicals in gaseous electronics studies. It produces a high degree of ionization and a large amount of molecular dissociation without undue heating of the background gas. It also has no need for internal electrodes, thus making it possible to construct reaction vessels which are simpler, free from contamination, and less subject to damage.
The purpose of a discharge cavity as used in accordance with this invention is to transfer power from a microwave source to a reactant gas, which is conducted through a quartz tube to a vacuum chamber. A resonant structure is used to increase the electric field in the gas. In order to match the impedance of this resonant structure to the waveguide of the microwave power supply, some sort of coupling device (such as a triple stub tuner) is used. When the impedance is matched, the power reflected from the microwave application is minimized. This is desirable since a decrease in the reflected power indicates an increase in efficiency of the applicator. Since the properties of the discharge change with pressure and with the particular reactant gas, it is necessary to provide both tuning and matching adjustments to obtain efficient operation over a wide range of discharge condition.